＜prologue＞
I started a blog called “The Baby Boomer Generation’s Miscellaneous Blog”（Dankai-sedai no garakutatyou:団塊世代の我楽多（がらくた）帳） in July 2018, about a year before I fully retired. More than six years have passed since then, and the number of articles has increased considerably.
So, in order to make them accessible to people who don’t understand Japanese, I decided to translate my past articles into English and publish them.
It may sound a bit exaggerated, but I would like to make this my life’s work.
It should be noted that haiku and waka （Japanese short fixed form poems） are quite difficult to translate into English, so some parts are written in Japanese.
If you are interested in haiku or waka and would like to know more, please read introductory or specialized books on haiku or waka written in English.
I also write many articles about the Japanese language. I would be happy if these inspire more people to want to learn Japanese.
my blog’s URL:団塊世代の我楽多（がらくた）帳 | 団塊世代が雑学や面白い話を発信しています
my X’s URL:団塊世代の我楽多帳（@historia49）さん / X
<Added 12/4/2020> Hayabusa 2 will finally return to Earth on 12/6!
<Added on July 11, 2019> It has been reported that Hayabusa 2 has succeeded in collecting soil for the second time and is scheduled to return at the end of 2020. We will be watching the analysis work and its results.
Recently, I have come across people who seem to be Christian missionaries standing on the streets of Osaka, holding up placards that read “The Origin of Life.” The placards read, “Would you like to think together about the origin of life?” They were, if anything, people with a polite demeanor.
They were probably trying to preach about a “Creator” using the Bible, but the question that arose in my mind was, “Do these people really believe such a thing?”
This is a topic that I have been interested in since I read a book called “The Origin of Life” by the Soviet biochemist Oparin (1894-1980), which was recommended to me by a biology professor in my university days. His theory was the “chemical evolution theory.”
１．What is the “origin of life”?
“Origin of life” refers to the process by which the first life on Earth was born and organisms evolved from non-living matter. Theories and theories on this subject are called “Abiogenesis.”
２．Theories about the “origin of life”
People have been asking the question “When, where, and how did life originate?” and coming up with explanations (hypotheses) for this question since ancient times.
In ancient times, this was explained through “myths.” The same thing has been done in various religions, and continues to be done to this day.
（1）Ancient Greece
The philosopher Thales (c. 624 BC – c. 546 BC) believed that the “origin (arche) of all things” was “water.” Heraclitus (c. 540 BC – c. 480 BC) thought it was “fire,” and Pythagoras (582 BC – 496 BC) thought “numbers” were the arche. The natural philosopher Empedocles (c. 490 BC – c. 430 BC) thought the four elements of “earth, water, fire, and air” were the arche.
Aristotle (384 BC – 322 BC) observed and dissected various animals and came to the conclusion that “some living things are born from parents, while others arise all at once from matter,” and proposed the theory of spontaneous generation. He explained that the “germ of life,” which is the basis of life, is spread throughout the world, and that this germ of life organizes matter to form life. This theory is called the “germ theory.”
（2）Judaism and Christianity
In the Book of Genesis in the Jewish Bible (Old Testament), the creation of the heavens and the earth took six days, and God rested on the seventh day. God created light on the first day, the sky and water on the second day, plants on the third day, the sun, moon, and stars on the fourth day, fish and birds on the fifth day, and animals, livestock, and humans in the image of God on the sixth day.
The Jewish Bible has also been passed down in Christianity as the Old Testament, so this view of life and the world is widely believed in Christian countries as well.
However, for those of us who already know the theory of evolution, the idea that God created humans is a complete lie. Well, it’s a myth, so it can’t be helped…
（3）History of research into “spontaneous generation”
In the 16th and 17th centuries, Paracelsus (1493-1541) of Switzerland and Helmont (1579-1644) of the Netherlands claimed that mice, frogs, eels, and other creatures could arise from inanimate objects.
The Italian Redi (1626-1697) proved through experiments that “fish that are not infested with flies do not develop maggots.”
The Dutchman Leeuwenhoek (1632-1723) invented the microscope and discovered microorganisms and cells in 1674.
The French scientist Pasteur (1822-1895) proved through experiments that there are a large number of invisible microorganisms (mold and bacterial spores) floating in the air.
（4）”Chemical evolution theory”
There was a time when it was thought that before life first appeared on Earth, no organic matter existed, and that the first organisms to appear were lithotrophic microorganisms.
However, in the 20th century, some scholars began to believe that “organic matter must have accumulated before the emergence of the first life.” Oparin was the first to propose this theory. In his book “The Origin of Life” (1922), he put forward the hypothesis that “organic matter accumulated from inorganic matter, and life was born through a reaction of the organic matter.” This is the “chemical evolution theory.”
（5）”World Hypothesis”
Since the 1950s, there has been debate as to which of the three substances – DNA (which stores genetic information), RNA (which acts as an intermediary), or protein – served as the template for the first life after chemical evolution. There are three hypotheses: the “DNA world hypothesis,” the “RNA world hypothesis,” and the “protein world hypothesis,” but there is no consensus yet.
（6）”Panspermia hypothesis”
This is a hypothesis that “the seeds of life are widespread in outer space” and “the first life came from outer space (life did not originate on Earth itself).” The original version of this theory was proposed in 1787 by the Italian Spallanzani (1729-1799).
This name was coined by the Swedish scientist Arrhenius (1859-1927) in 1906. Arrhenius stated that “the origin of life is not native to Earth, but is a result of microbial spores that originated on other celestial bodies and traveled through space to reach Earth.”
However, this theory has not yet provided a fundamental explanation for the origin of life.
In any case, there is a possibility that life and living things may exist in the galaxy outside of our solar system, and there are even more unknowns about the entire universe outside of our galaxy.
The number of “galaxies” in the universe was previously thought to be about 200 billion, but recent observations by the Hubble Space Telescope have revealed that there are actually more than 2 trillion. That’s a mind-boggling number.
３．Survey of asteroid Ryugu by collecting rocks using Hayabusa 2
Just the other day, JAXA’s (Japan Aerospace Exploration Agency) asteroid probe “Hayabusa 2” successfully landed on the asteroid “Ryugu.” “Ryugu” is located 340 million km away from Earth, and it took four years to reach there. It is said that the probe will collect rock fragments, which are expected to provide clues about the formation of the solar system and the origin of life.
It is said to be an asteroid that was formed 4.6 billion years ago, just like Earth, but it appears to be made up of only rocks without water, so I have doubts as to whether it will actually help solve the mystery of the “origin of life.”